1. Field of the Invention
The present invention relates to a maintenance liquid of an ink-jet discharging device which is used for applying a photo-curable composition onto a substrate or a mold in photo-imprint methods which saves to transfer a surface shape of a mold on a surface of a substrate.
2. Description of the Related Art
Imprint technology is a development advanced from embossing technology well known in the art of optical disc production, which comprises pressing a mold original with an embossed pattern formed on its surface (this is generally referred to as “mold”, “stamper” or “template”) against a resist to thereby accurately transfer the micro-pattern onto the resin through mechanical deformation of the resist. In this, when a mold is once prepared, then microstructures such as nanostructures can be repeatedly molded, and therefore, this is economical, and in addition, harmful wastes and discharges from this nanotechnology are reduced. Accordingly these days, this is expected to be applicable to various technical fields.
Two methods of imprint technology have been proposed; one is a thermal imprint method using a thermoplastic resin as the material to be worked (for example, see S. Chou, et al., Appl. Phys. Lett. Vol. 67, 3114 (1995)), and the other is a photoimprint method using a photo-curable composition (for example, see M. Colbun, et al., Proc. SPIE, Vol. 3676, 379 (1999)). In the photoimprint method where a curable composition for photoimprints is photo-cured by photoirradiation through a transparent mold or a transparent substrate, the transferring material does not require heating in pressing it against the mold, and therefore the method enables room-temperature imprinting.
For the imprint methods as above, proposed are applied technologies mentioned below.
In the first technology, the molded pattern itself has a function, and is applied to various elements in nanotechnology and to structural members. Its examples include various micro/nano optical elements and high-density recording media, as well as structural members in optical films, flat panel displays, etc. The second technology is for hybrid-molding of microstructures and nanostructures, or for construction of laminate structures through simple interlayer positioning, and this is applied to production of μ-TAS (micro-total analysis system) and biochips. In the third technology, the formed pattern is used as a mask and is applied to a method of processing a substrate through etching or the like. In these technologies, high-precision positioning is combined with high-density integration; and in place of conventional lithography technology, these technologies are being applied to production of high-density semiconductor integrated circuits and transistors in liquid-crystal displays, and also to magnetic processing for next-generation hard discs referred to as patterned media. Recently, practical realization of imprint methods concerning those applications including the above technologies has become active.
As one example of imprint technology, hereinunder described is an application to production of high-density semiconductor integrated circuits. The recent development in micro-patterning and integration scale enlargement in semiconductor integrated circuits is remarkable, and high-definition photolithography for pattern transfer for realizing the intended micro-patterning is being much promoted and advanced in the art. However, for further requirement for more definite micro-patterning to a higher level, it is now difficult to satisfy all the three of micro-pattern resolution, cost reduction and throughput increase. Regarding this, as a technology of micro-patterning capable of attaining at a low cost, imprint lithography technique, especially nanoimprint lithography (photonanoimprint method) is proposed. For example, U.S. Pat. Nos. 5,772,905 and 5,259,926 disclose a nanoimprint technology of using a silicon wafer as a stamper for transferring a microstructure of at most 25 nm. This application requires micro-patternability on a level of a few tens nm and high-level etching resistance of the micro-pattern functioning as a mask in substrate processing.
In next-generation hard disc drives (HDD), there are proposed technologies of discrete track media and bit patterned media of filling the distance between the adjacent tracks with a non-magnetic material to thereby physically and magnetically separate the tracks. As a method of forming the magnetic or non-magnetic pattern in production of these media, application of nanoimprint technology is proposed. The application also requires micro-patternability on a level of a few tens nm and high-level etching resistance of the micro-pattern functioning as a mask in substrate processing.
In production of a flat display such as liquid-crystal displays (LCD) and plasma display panels (PDP), with the recent tendency toward large-sized substrates for high-definition microprocessing thereon, production of thin-film transistors (TFT) and electrode plates, and application of photoimprint technology to transparent protective film materials described in JP-A-2005-197699 and JP-A-2005-301289, or to spacers described in JP-A-2005-301289 are being under investigation.
Therefore, photoimprint lithography has become specifically noted these days as an inexpensive lithography technology capable of being substituted for conventional photolithography.
Further, imprint lithography is useful also in formation of permanent films in optical members such as microelectromechanical systems (MEMS), sensor devices, gratings, relief holograms, etc.; optical films for production of nanodevices, optical devices, flat panel displays, etc.; polarizing elements, thin-film transistors in liquid-crystal displays, organic transistors, color filters, overcoat layers, pillar materials, rib materials for liquid-crystal alignment, microlens arrays, immunoassay chips, DNA separation chips, microreactors, nanobio devices, optical waveguides, optical filters, photonic liquid crystals, reflection-preventing structures (moth-eye) etc.
In the photo-imprint method, a pattern may be obtained by placing a photo-curable composition on a substrate or mold, irradiating light onto the photo-curable composition held between the substrate and the mold so as to cure the photo-curable composition, and then releasing the mold. Various techniques of placing the photo-curable composition onto the substrate have been proposed. Published Japanese Translation of PCT International Publication for Patent Application No. 2005-533393 proposes a method of coating the photo-curable composition by an ink-jet device. Since the method of coating making use of the ink-jet device is capable of coating a resist in a discrete manner on the substrate, while specifying positions of landing of resist droplets, so that only a necessary amount of the resist may be placed depending on pattern density, and thereby the thickness of the obtained film may be made uniform.